阅读说明：本技术 一种用于丙烷催化脱氢制丙烯的负载型铂系催化剂及其制备方法 (Supported platinum catalyst for preparing propylene by catalytic dehydrogenation of propane and preparation method thereof ) 是由 王广建 宋宁 韩德志 王峰忠 邴连成 王芳 于 2020-04-10 设计创作，主要内容包括：本发明公开了一种用于丙烷催化脱氢制丙烯的负载型铂系催化剂及其制备方法,涉及丙烷脱氢制备丙烯的催化技术领域,为解决现有催化剂高温使用过程中活性组分易迁移、聚集和积碳失活、整体催化剂活性较低和稳定性较差的问题,提供一种负载型铂系催化剂。该催化剂的组分为Pt-Sn/N-Al<Sub>2</Sub>O<Sub>3</Sub>,N为金属改性助剂Na、K、Ce、La。按质量百分比计：Pt0.5％～0.8％,Sn0.1％～0.2％,N0.5％～3％,余量为三维有序大孔Al<Sub>2</Sub>O<Sub>3</Sub>。制备方法：制备PMMA模版剂,然后将适量模板剂倒入含Al(NO<Sub>3</Sub>)·9H<Sub>2</Sub>O的95％乙醇溶液中,经浸渍、抽滤、干燥和焙烧得到三维有序大孔Al<Sub>2</Sub>O<Sub>3</Sub>载体；在Al<Sub>2</Sub>O<Sub>3</Sub>载体上负载硝酸钠、硝酸钾、硝酸铈或硝酸镧溶液,经干燥、焙烧后,将Pt和Sn组分以等体积浸渍的方式负载到改性载体上,经干燥、焙烧后制得Pt-Sn/N-Al<Sub>2</Sub>O<Sub>3</Sub>催化剂。三维有序大孔Al<Sub>2</Sub>O<Sub>3</Sub>载体负载型催化剂具有较好的转化率、选择性和稳定性。(The invention discloses a supported platinum catalyst for preparing propylene by propane catalytic dehydrogenation and a preparation method thereof, relates to the technical field of catalysis for preparing propylene by propane dehydrogenation, and provides the supported platinum catalyst for solving the problems of easy migration, aggregation and carbon deposition inactivation of active components, low activity and poor stability of the whole catalyst in the high-temperature use process of the existing catalyst. The catalyst comprises the components of Pt-Sn/N-Al 2 O 3 And N is metal modification auxiliary agents Na, K, Ce and La. The weight percentage of the material is as follows: 0.5 to 0.8 percent of Pt0, 0.1 to 0.2 percent of Sn0.5 to 3 percent of N, and the balance of three-dimensional ordered macroporous Al 2 O 3 . The preparation method comprises the following steps: preparing PMMA template agent, then pouring a proper amount of template agent into the mold containing Al (NO) 3 )·9H 2 In a 95% ethanol solution of O,the three-dimensional ordered macroporous Al is obtained by dipping, suction filtration, drying and roasting 2 O 3 A carrier; in Al 2 O 3 Loading sodium nitrate, potassium nitrate, cerium nitrate or lanthanum nitrate solution on a carrier, drying and roasting, loading Pt and Sn components on a modified carrier in an isometric impregnation mode, drying and roasting to obtain the Pt-Sn/N-Al 2 O 3 A catalyst. Three-dimensional ordered macroporous Al 2 O 3 The carrier supported catalyst has better conversion rate, selectivity and stability.)

1. A supported platinum catalyst for preparing propylene by propane catalytic dehydrogenation is characterized in that the catalyst comprises Pt-Sn/N-Al₂O₃Pt as the active metal and Sn/N as the aidN is selected from sodium nitrate, potassium nitrate, cerium nitrate, lanthanum nitrate and Al₂O₃Is a three-dimensional ordered macroporous carrier; the components are calculated according to the weight percentage: 0.5 to 0.8 percent of Pt, 0.1 to 0.2 percent of Sn, 0.5 to 3 percent of N and the balance of three-dimensional ordered macroporous Al₂O₃。

2. The method for preparing the supported platinum-based catalyst for preparing propylene by propane dehydrogenation according to claim 1, comprising the following steps:

1) preparing a PMMA template agent or a PS template agent: adding deionized water and methyl methacrylate into a 1000mL four-neck flask, introducing nitrogen for protection, adding an emulsifier, heating to above 70 ℃, adding an initiator, continuously reacting for more than 1 hour, taking out the emulsion, cooling to room temperature, centrifugally assembling, and drying in a water bath to obtain PMMA with a Bragg light effect; preparing a PS template agent by using styrene to replace methyl methacrylate according to the same method; pouring PMMA template or PS template into the mold containing Al (NO)₃)·9H₂Soaking in 95% ethanol solution of O, filtering, drying and roasting to obtain three-dimensional ordered macroporous Al₂O₃A carrier;

2) respectively soaking sodium, potassium nitrate, cerium nitrate and lanthanum nitrate solution in the three-dimensional ordered macroporous Al prepared in the step 1) by adopting an isometric soaking method₂O₃Drying and roasting the carrier to obtain the modified catalyst carrier N-Al₂O₃；

3) The modified catalyst carrier is N-Al₂O₃Co-dipping the catalyst in a mixed solution of an auxiliary Sn and an active component Pt, and drying and roasting to obtain the supported platinum catalyst applied to preparing propylene by propane dehydrogenation.

3. The method for preparing a supported platinum-based catalyst for propane dehydrogenation to propylene according to claim 2, wherein the calcination temperature in step 1) is 550 to 800 ℃.

4. The method for preparing a supported platinum-based catalyst for propane dehydrogenation to propylene according to claim 2, wherein the calcination temperature in step 2) is 550 to 650 ℃.

5. The method for preparing a supported platinum-based catalyst for propane dehydrogenation to propylene according to claim 2, wherein the calcination temperature in step 3) is 550 to 650 ℃.

6. The method for preparing a supported platinum-based catalyst for propane dehydrogenation to propylene according to claim 2, wherein the impregnation time in step 2) is 4 to 8 hours.

7. The method for preparing the supported platinum-based catalyst for preparing propylene by propane dehydrogenation according to claim 2, wherein in the step 3), the drying condition is drying in an oven at 80-100 ℃ for 6-10 h.

8. The method for preparing the supported platinum-based catalyst for preparing propylene by propane dehydrogenation according to claim 2, wherein in the step 3), the calcination time is 4-6 h.

9. The method for preparing a supported platinum-based catalyst for propane dehydrogenation to produce propylene according to claim 2, wherein the emulsifier in step 1) is sodium lauryl sulfate and the initiator is potassium persulfate.

Technical Field

The invention relates to a catalytic technology for preparing propylene by propane dehydrogenation, in particular to a supported platinum catalyst for preparing propylene by propane catalytic dehydrogenation and a preparation method thereof.

Background

Propylene (CH)₃-CH＝CH₂) Is an important petrochemical basic raw material, is mainly used for producing products such as polypropylene, acrylonitrile, propylene oxide, acrylic acid, butanol, octanol, cumene, isopropyl acid and the like, and has a steadily increasing trend of the world demand for propylene. At present, propylene supply mainly comes from ethylene prepared by naphtha cracking and byproducts generated in the petroleum catalytic cracking process, and due to the influence of factors such as petroleum supply, lighter catalytic cracking feed and the like, the yield of propylene is reduced, so that the propylene gap is increased, and the propylene prepared by the traditional process cannot meet the market demand of the current world on propylene. The propane gas in China is rich in resources and low in price, and the propane with abundant and low price is subjected to dehydrogenation catalytic reaction to prepare the propylene with high added value which is in short supply in the market, so that the method has important practical significance.

At present, the technology for preparing propylene by propane dehydrogenation mainly comprises the following steps: 1) catalytic dehydrogenation 2) non-oxidative catalytic dehydrogenation 3) membrane reactor dehydrogenation. Among them, non-oxidative catalytic dehydrogenation is attracting attention because of its high catalytic safety and good stability. The preparation of propylene by catalytic dehydrogenation of propane is a strong endothermic reaction, which is limited by thermodynamic equilibrium and needs to be carried out under low pressure and high temperature conditions in order to obtain higher conversion rate. However, the high temperature will cause the propane to be easily cracked to smallThe molecule causes the selectivity of the catalyst to be reduced, and simultaneously, the generated olefin is easy to polymerize and cyclize into macromolecules to cause carbon deposition and inactivation of the catalyst. Therefore, the development of a propane dehydrogenation propylene preparation catalyst with high activity, high selectivity and high stability is the key of non-oxidative catalytic dehydrogenation. In this regard, researchers have conducted a great deal of research. For example, U.S. Pat. No. 4, 4,506,032 uses Pt-Sn-K-Cl/γ -Al₂O₃The catalyst is prepared by soaking a chloroplatinic acid solution and a potassium nitrate solution in steps by using an Sn-doped alumina carrier, drying and roasting the solution, and then injecting chlorine into the solution, wherein the prepared catalyst is used for dehydrogenation of low-carbon alkane. US patent 4,595,673 on Pt-Sn-K-Li-Cl/gamma-Al₂O₃The catalyst is prepared by co-soaking chloroplatinic acid and lithium nitrate solution in Sn-doped alumina carrier, drying, roasting, soaking in potassium nitrate solution, and drying and roasting. The procedure is complicated and the catalytic repeatability is poor. The catalyst disclosed in the Chinese patent CN200710025372.X is a preparation method of impregnating a platinum-tin component on an alumina modified mesoporous molecular sieve serving as a carrier, wherein the conversion rate of propane is only 17 percent, and the selectivity of propylene is 93 percent; chinese patent CN101066532A reports a preparation method of a ZSM-5 molecular sieve skeleton carrier containing Sn for propane dehydrogenation propylene catalyst, the catalyst shows higher selectivity and stability, but the conversion rate is relatively lower, the preparation process of the ZSM-5 molecular sieve containing Sn is longer, the energy consumption is large, the content of each metal component is relatively higher, and the preparation cost of the catalyst is correspondingly increased.

Disclosure of Invention

Aiming at the problems of easy migration, aggregation and carbon deposition inactivation of active components, low activity and poor stability of the whole catalyst and gradual reduction of selectivity in the operation process of the existing catalyst in the high-temperature use process, the invention provides a supported platinum catalyst which is used for preparing propylene by propane dehydrogenation by a non-oxidation catalysis method.

The technical scheme adopted by the invention is as follows:

the supported platinum catalyst applied to the preparation of propylene by propane dehydrogenation comprises the components of Pt-Sn/N-Al₂O₃Wherein, metal Pt is used as active metal, Sn/N is used as auxiliary agent, N is selected from sodium nitrate, potassium nitrate, cerous nitrate, lanthanum nitrate and Al₂O₃Is a three-dimensional ordered macroporous carrier, and comprises the following components, by weight, 0.5-0.8% of Pt, 0.1-0.2% of Sn, 0.5-3% of N, and the balance of three-dimensional ordered macroporous Al₂O₃。

The preparation method of the supported platinum catalyst applied to preparing propylene by propane dehydrogenation comprises the following steps:

1) preparation of three-dimensional ordered macroporous Al₂O₃Firstly, preparing a PMMA template agent or a PS template agent: adding a certain amount of deionized water and methyl methacrylate into a 1000mL four-neck flask, introducing nitrogen for protection, adding a trace amount of emulsifier, heating to above 70 ℃, adding a proper amount of initiator, continuously reacting for more than 1 hour, taking out the emulsion, cooling to room temperature, washing for multiple times, carrying out centrifugal assembly, and drying in a water bath to obtain a PMMA template agent with a Bragg light effect; the PS template agent with the Bragg light effect is prepared by adopting the method by using (styrene) to replace methyl methacrylate; then pouring proper amount of PMMA template agent or PS template agent into the mold containing certain amount of Al (NO)₃)·9H₂Soaking in 95% ethanol solution of O, filtering, drying and roasting to obtain three-dimensional ordered macroporous Al₂O₃The carrier is the carrier of the catalyst for preparing propylene by propane dehydrogenation;

2) dipping the three-dimensional ordered macroporous Al prepared in the step 1) in a sodium nitrate, potassium nitrate, cerium nitrate and lanthanum nitrate solution by adopting an isometric dipping method₂O₃Drying and roasting the carrier to obtain the modified catalyst carrier N-Al₂O₃；

3) An isovolumetric impregnation method is adopted to load an active component Pt and an auxiliary agent Sn component to the modified catalyst carrier N-Al in a co-impregnation or step-by-step impregnation mode₂O₃Drying and roasting to obtain the supported platinum applied to preparing propylene by propane dehydrogenationIs a catalyst.

Further, in the step 1), the drying temperature may be 60 to 100 ℃;

further, the roasting temperature in the step 1) can be 550-800 ℃.

Further, in the step 2), the roasting temperature may be 550 to 650 ℃.

Further, the dipping time in the step 2) is 4-8 h;

further, the drying condition of the step 2) is drying for 6-10 hours in an oven at 60-100 ℃;

further, the roasting condition of the step 3) is roasting for 4-6 hours in a muffle furnace at 550-650 ℃.

The supported platinum catalyst is applied to the reaction of preparing propylene by propane dehydrogenation, and comprises the following specific steps:

1) placing 3.0-5.0 g of the supported platinum catalyst in a fixed bed stainless steel reaction tube, heating to 450-570 ℃ at a heating rate of 2 ℃/min at room temperature in a 10% hydrogen atmosphere, and carrying out reduction activation for 6-10 h, wherein the flow rate of hydrogen is 140-160 mL/min;

2) after the reduction is finished, raising the temperature of a bed layer of the reaction tube to 550-620 ℃ under the normal pressure condition, and introducing pure propane gas for reaction, wherein the flow rate of the propane gas is 60-100 mL/min.

The method comprises the steps of firstly preparing a three-dimensional ordered macroporous alumina precursor by using a colloidal crystal template method, drying and roasting to prepare a carrier of a propylene catalyst prepared by propane dehydrogenation, then impregnating N components of a modification auxiliary agent, namely sodium nitrate, potassium nitrate, cerium nitrate and lanthanum nitrate, on the alumina carrier by using an isometric impregnation method, and drying and roasting to obtain the modified catalyst carrier, namely N-Al₂O₃. And loading the Pt and Sn components by an equal-volume co-impregnation method or a step-by-step impregnation method.

The supported platinum catalyst applied to the preparation of propylene by propane dehydrogenation can effectively catalyze propane dehydrogenation to prepare propylene under mild conditions, the propane conversion rate is still higher than 35.5%, the selectivity of propylene is still higher than 87%, carbon deposition on the catalyst is less, the activity is slowly reduced, and the catalyst still has good catalytic activity after multiple regeneration after reaction for 10 hours in pure propane atmosphere without any diluent gas under the condition of 550-600 ℃.

Compared with the prior art, the invention has the following advantages:

1) the preparation method comprises the steps of firstly, when three-dimensional ordered macroporous alumina is used as a carrier, the carrier has good carrier structure performance, active components can be well loaded and uniformly dispersed on the carrier, the active components are efficiently utilized, after the auxiliary agent is added, the interaction between the active components and the carrier can be effectively enhanced, the active components do not migrate in the high-temperature reaction process, and the sintering inactivation of the active components is reduced. And after the modification of the auxiliary agent, the surface acidity of the alumina carrier can be obviously improved, the increase of side reactions and the deepening of carbon deposition caused by the influence of an acid position in the reaction process of the catalyst are prevented, the stability of the catalyst is effectively improved, the mass transfer resistance of a target product on the catalyst is reduced, and the separation of reactants and the product is enhanced.

2) In the invention, the catalyst is prepared by adopting an isometric saturated impregnation method, so that the using amount of each metal component is reduced, the utilization efficiency of the metal components is improved, the production cost is reduced, and the method is suitable for large-scale production and industrial application.

3) The catalyst has high reaction activity, high propane conversion rate and propylene selectivity, less carbon deposit on the catalyst, slow reduction of catalyst activity and strong regeneration.

Drawings

FIG. 1 is an SEM electron micrograph of a PMMA template prepared;

FIG. 2 is an SEM electron microscope image of a three-dimensional ordered catalyst for catalytic dehydrogenation of propane to propylene in example 2 after calcination;

FIG. 3 is a flow diagram of the preparation of the catalyst.

Detailed Description

The invention is further described below with reference to the figures and examples.

Firstly, a chloroplatinic acid solution and a stannous chloride solution are prepared.

Preparing a chloroplatinic acid solution: dissolving 2g of chloroplatinic acid in deionized water, transferring the solution into a 50mL volumetric flask, adding the deionized water to the scale mark of the volumetric flask, and placing the volumetric flask in the shade for later use.

Preparing a stannous chloride solution: dissolving 2g of stannous chloride in 10mL of concentrated hydrochloric acid, transferring the solution to a 100mL volumetric flask after the solution, and adding deionized water to the scale mark of the volumetric flask for later use.